1. Field of the Invention
The present invention relates to a process and composition for the surface treatment of titanium and titanium alloys. More particularly, the invention relates to a process for providing a surface film which facilitates the working of such materials.
2. Statement of Related Art
Fluoride-based treatment solutions are used as substrate conversion coating solutions for the formation of lubricating films on titanium or its alloys, for example, as described in U.S. Pat. No. 4,004,064 and Japanese Patent Publication No. 44-28967. The conversion coating solution disclosed in Japanese Patent Publication No. 44-28967 contains (1): hydrofluoric acid or alkalifluoride, (2): sulfuric acid, nitric acid or an alkali salt thereof, and (3): a fluoride, sulfate or nitrate of a metal such as manganese, molybdenum or zinc. These compositions are used as a substrate for a lubricant for drawing work.
With the treatment solution of the invention disclosed in Japanese Patent Publication No. 44-28967, it is not possible to form a film that displays satisfactory adhesion during working if titanium or a titanium alloy is subjected to heavy and complex and/or high speed cold working. It has also been found that problems of seizure, etc. occur during cold working of titanium or a titanium alloy on which a lubrication film has been formed since there is considerable fluctuation in the quality of films.